XENON ADSORPTION ON PT-PD ALLOY SURFACES - COMPARISON OF CALCULATIONSWITH EXPERIMENTAL-DATA

The adsorption of Xe on Pt-Pd alloy surfaces was studied using UV phot oelectron spectroscopy. The alloy surfaces of different composition we re prepared by depositing a film on the Pd(110) substrate and annealin g to increasing temperatures. The initial Pt film exhibited a (110)(1 x 2) reconstruction. Increasing amounts of Pd diffusing through the Pt overlayer turned the surface structure back into an unreconstructed ( 110) topography. As an example, the Xe(5p3/2,1/2) UPS spectra obtained for different Xe coverages on a Pt-5% Pd alloy surface could be fitte d with up to 4 Xe adsorption states taking the corresponding spectra f rom the clean Pt(110)(1 x 2) and Pd(110) surfaces as references. The r elative adsorption energies (E(ad)) of Xe atoms at various sites on th e alloy surface are discussed in the light of Lennard-Jones Xe-Pt and Xe-Pd pair-potential calculations.